We just don't get it, there are so many other things you could say.
The entire ensemble comes in a tattered heathered gray, leaving you looking pale and, well, dead. We aren't really sure why saying boo is a thing at all, to be honest. If you wanted to add to the scare you could say something scary like "Your soul is mine!" or "Your dead!", but we still just assume that ghosts would say boo. FUN DETAILS This whole dress is downright spooky! It's not like we have done our research, we haven't been searching for an answer, it just seems like their might be other stuff worth yelling if you're a ghost, you know? Saying boo doesn't actually mean anything, really, you might as well just grunt or yell.